A127790(n)/2.

Terms

a(0) =0a(1) =1a(2) =4a(3) =12a(4) =32a(5) =74a(6) =156a(7) =310a(8) =580a(9) =1035a(10) =1780a(11) =2956a(12) =4764a(13) =7487a(14) =11492a(15) =17274a(16) =25492a(17) =36979a(18) =52812a(19) =74372a(20) =103364a(21) =141927a(22) =192724a(23) =258982a(24) =344652a(25) =454544a(26) =594392a(27) =771084a(28) =992852a(29) =1269377